The present invention is directed toward a single stage hydrocracking process for the simultaneous production of jet fuel and diesel fuel. Suitable feed stocks include vacuum gas oils, atmospheric gas oils and any other hydrocarbon charge stocks boiling at a temperature greater than about 500.degree. F. Hydrocracking, also commonly referred to as "destructive hydrogenation", is distinguished from the simple addition of hydrogen to unsaturated bonds between carbon atoms, since it effects definite changes in the molecular structure of the hydrocarbons being processed. Hydrocracking may, therefore, be designated as cracking under hydrogenation conditions such that the lower-boiling products of the cracking reactions are substantially more saturated than when hydrogen, or material supplying hydrogen, is not present. Although some hydrocracking processes are conducted thermally, the preferred processing technique involves the utilization of a catalytic composite possessing a high degree of hydrocracking activity. In virtually all hydrocracking processes, whether thermal or catalytic, controlled or selective cracking is desirable from the standpoint of producing an increased yield of liquid product having improved, advantageous physical and/or chemical characteristics.
Selective hydrocracking is especially important when processing hydrocarbons and mixtures of hydrocarbons which boil at temperatures above the gasoline and/or the middle-distillate boiling range; that is, hydrocarbons and mixtures of hydrocarbons, as well as the various hydrocarbon fractions and distillates, having a boiling range indicating an initial boiling point of from about 600.degree. F. to 700.degree. F., and an end boiling point as high as 1000.degree. F. or more. Selective hydrocracking of such hydrocarbon fractions results in greater yield of hydrocarbons boiling within and below the middle-distillate boiling range. Selective hydrocracking involves the splitting of a higher-boiling hydrocarbon molecule into two molecules, both of which are normally liquid hydrocarbons.
A major disadvantage of nonselective or uncontrolled hydrocracking, is the more rapid formation of increased quantities of coke and other heavy carbonaceous material which becomes deposited upon the catalyst and decreases, or destroys, the activity thereof to catalyze the desired reactions. Such deactivation results in a shorter acceptable processing cycle or period, with the inherent necessity for more frequent regeneration of the catalyst, or total replacement thereof with fresh catalyst.
The utilization of the process of the present invention permits milder reaction conditions to be employed in the catalytic reaction zone which facilitates the maximization of selectivity during hydrocracking and the minimization of coke formation on the catalyst.